Linerless labels are becoming increasingly more popular due to the inherent advantages associated therewith, as a result of not requiring a separate release sheet. Typical linerless labels are disclosed in U.S. Pat. Nos. 5,292,713 and 4,978,415, and U.S. Pat. Nos. 5,354,588 and 5,417,783 and co-pending application Ser. Nos. 07/907,511 filed Jul. 1, 1992 and 08/078,918 filed Jun. 2, 1993, the disclosures of which are hereby incorporated by reference herein.
There are several major types of linerless labels that are common; repositional adhesive labels, removable adhesive labels and permanent adhesive labels. Different types of equipment are necessary in order to make these different types of linerless labels because of the widely divergent characteristics, drying methods, and the like of the adhesives and release coats that are used in the manufacture thereof. Since it is highly desirable to print or otherwise image the labels during manufacture thereof, equipment costs can be high to construct and maintain different equipment lines. Therefore if the demand for the different types of labels varies significantly, as often occurs in practice, some equipment may be left idle while other equipment is stressed to capacity.
According to the present invention a method and apparatus are provided which allow the alternative construction of either permanent adhesive or repositional adhesive labels utilizing the same equipment. According to the invention the changeover time from the manufacture of one type of labels to the other is short, and many of the components can be used for both types of labels despite their significant differences. This allows a minimum expenditure of capital and maximum flexibility in accommodating market needs.
According to one aspect of the present invention, apparatus is provided for alternatively manufacturing permanent adhesive or repositional adhesive linerless labels. The apparatus includes a plurality of components spaced from each other in a first direction which comprises the direction of travel of a web acted upon by the apparatus to produce the linerless labels. The components comprise the following: An indicia applying station. A first coating station for applying the tie coat in the construction of repositional adhesive labels. A second coating station for optionally applying a barrier coat in the construction of permanent adhesive labels, or repositional adhesive in the construction of repositional adhesive labels. A third coating station for applying a release coat in the construction of repositional adhesive labels. A dryer capable of drying both sides (faces) of a web at the same time, located downstream of the second coating station. A fourth coating station for applying a release coat in the construction of permanent adhesive labels. A release coat curing station for curing a release coat in the construction of permanent adhesive labels. And, a permanent adhesive application station.
The permanent adhesive application station includes a heated slot die head for applying hot melt adhesive. The die head has a length aligned with the web width, and provides a heat uniformity of .+-. five degrees F across the length, and an adhesive coat thickness of about .+-. 0.0001 inch across the length. Typically the coating thickness is about 0.0005-0.001 inches.
The heated slot die head has a main portion with die lips, having a length of about 16 inches and includes nine substantially uniformly spaced cartridge heaters along the length in a substantially straight line configuration having first and second ends. At least first and second temperature sensors are provided, one located between the second and third cartridges from each of the first and second ends of the straight line configuration. The head also includes a valve block and further comprises at least one cartridge heater and at least one temperature sensor disposed in the valve block. Control of the valve block cartridge heater(s) is independent of control of the cartridge heaters in the main portion.
Preferably the die lips are flat (having been ground that way) and form a slot between them through which the adhesive flows, e.g. to a thickness of about 0.0005-0.001 inches when provided as a coat on the web. The lips typically have a quadrate (e.g. rectangular) shape in cross section and each has a thickness of about 0.06 inches, and the slot between them has a thickness (corresponding to the spacing between the lips) of about 0.012 inches. Heat insulation is also provided to maintain heat and the uniformity of the heat across the die head, and also preferably the valve block.
The indicia applying section may comprise a variable intelligent imaging system such as ion deposition (e.g. MIDAX.RTM., Indigo, Xeikon), ink jet, or like imaging equipment, and at least one print station such as that typically provided on an in-line web printing press, such as a Webtron press, available from Webtron of Fort Lauderdale, Fla. If four color printing of both sides of the linerless labels is desired, eight print stations will be provided.
The components may be in the sequence recited above (with the imaging system being the most upstream component and the permanent adhesive station the most downstream component in the first direction), or the sequence can be changed, as long as there is appropriate drying or curing of the various coats once applied.
A web unwind assembly is typically provided upstream of the variable intelligent imaging system in the first direction, and a web rewind assembly downstream of the permanent adhesive application station. A perf station for applying perfs in a second direction generally perpendicular to the first direction is also preferably provided typically before the second coating station. A video inspection station may be provided immediately adjacent and downstream of the perf station. A sheeter and longitudinal perf station may be disposed between the permanent adhesive station and the rewind assembly, and a metered infeed assembly may be provided between the unwind assembly and the imaging system.
The fourth coating station may comprise a UV silicone release coat application station. The release coat curing station may comprise a UV curing station including nitrogen inerted UV curing and an oxygen analyzer with a nitrogen flow control system. A turning mechanism may be associated with the variable intelligent imaging system and first coating station to allow two-sided imaging of a web used to produce the labels in a convenient manner, and bypass means (such as the diverter roll or rollers) may be provided for bypassing an individual component when not in use.
The invention also relates to a method of alternatively manufacturing either permanent adhesive linerless labels or repositional adhesive linerless labels utilizing common equipment. The method comprises the steps of automatically: (a) Continuously feeding a web of label substrate material having first and second faces so that it moves in a first direction. And while practicing step (a): (b) Imaging indicia on one or both of the faces of the web. Alternatively practicing step (c) or step (d) as follows: (c) If repositional adhesive linerless labels are being manufactured, applying and drying a tie coat to the first face of the web, applying a repositional adhesive to the first face of the web, applying a release coat to the second face of the web, and drying the release coat and repositional adhesive at the same time. (d) If permanent adhesive linerless labels are being manufactured, applying a barrier coat to the first face of the web, drying the barrier coat, and then applying a release coating over the barrier coat and curing the release coat, and applying a permanent adhesive to the second face. (e) Applying perfs to the web in a second direction substantially transverse to the first direction to define labels in the web. (f) Taking up the web after the practice of steps (b), (c) or (d), and (e); and (g) occasionally (e.g. periodically, intermittently, or typically simply when desired) changing over from step (c) to step (d), and vice versa. Step (b) is typically practiced using a flexo unit having at least one print cylinder. In that case there is the further step of immediately detaching the at least one print cylinder from the web when the common equipment is turned off. That is when a "stop" button on a control panel is pressed the print cylinders are immediately removed from ("thrown off") the web rather than waiting for the web to come to a natural stop. This reduces plate cleaning, web breaks, and waste, and improves print quality.
During the practice of step (c) a tie coat may be applied to the web first face prior to the repositional adhesive being applied to the first face. The barrier coat or the repositional adhesive may be applied by the same coater depending upon whether step (c) or step (d) is practiced. During the practice of step (c) the repositional adhesive and release coat are dried simultaneously by a two sided hot air dryer. Step (d) may be practiced by applying a UV silicone release coat, and UV curing release coat prior to the application of the permanent adhesive, which may be hot melt, water based or the like adhesives. Video inspection of the perfs formed after the practiced of step (e) may also be effected. The application of permanent adhesive and the barrier coat may be pattern coated or applied in a continuous format, depending on the particular application.
The invention also relates to a method of automatically manufacturing a web of permanent adhesive linerless labels from a web of substrate material having first and second faces. This method comprises the steps of: Imaging indicia on at least one face of the substrate. Optionally, perfing the substrate web to define labels. Alternatively, the labels may be severed from the web by a cutter and then fed to a sheeter to collect the cut labels in a stack. Applying a barrier coat to the first face of the substrate. Hot air drying the barrier coat. Applying a UV silicone release coat to the first face of the substrate. UV curing the UV silicon release coat. Applying a permanent adhesive to the second face of the substrate. And, taking up the web of linerless labels produced. The permanent adhesive applying step is preferably practiced by applying a hot melt permanent adhesive with a temperature uniformly of .+-. five degrees F across the width of the web, and with an adhesive coat thickness uniformity of .+-. about 0.0001 inches across the width of the web.
Permanent adhesive application is typically practiced using a heated slot die head as described above, and to apply an adhesive coating thickness of about 0.001 inches. The steps as recited above are preferably practiced sequentially. The repositionable adhesive and the tie coat may be pattern coated or applied in a continuous format, depending on the particular application.
The invention also contemplates a method of automatically manufacturing a web of repositional adhesive linerless labels from a web of substrate material having first and second faces. The method comprises the steps of: Imaging indicia on at least one face of the substrate. Optionally, perfing the substrate web to define labels. Applying a tie coat to the first face of the web and drying the tie coat. Applying a repositional adhesive to the first face of the substrate and a release coat to the second face. Simultaneously hot air drying the adhesive and release coats. And, taking up the web of repositional adhesive linerless labels produced. The repositional adhesive applying step is typically practiced using a flexographic unit having a print cylinder, and upon stopping of the practice of the imaging and repositional adhesive applying steps the print cylinder is provided in contact with the web a period of time (e.g. several seconds) only sufficient to wipe excessive adhesive off the print cylinder, and then the print cylinder is moved out of contact with the web. This prevents the excess adhesive from hardening on the unit, requiring the operator to chip it off. The steps recited above may be practiced sequentially.
It is the primary object of the present invention to provide a simple yet effective apparatus and method for the alternative manufacture of repositional adhesive linerless labels or permanent adhesive linerless labels. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.